I am going to buy myself a new AR for my retirement. It will be used for mainly prairie dog and other varmints and maybe some coyote hunting also. I already have a Vortex Viper HS 4-16x44 LR scope for it. I was pretty much settled on a Rock River Arms LAR 15 X-1 rifle in the tan color. The RRA's seem to get good reviews from hunters using them. I can get it for $1300 from a dealer on line with a 3 month or so wait. However, I keep seeing that many people recommend Colt as the "best" rifle. I have looked on Gun Broker and can find Colt Competition models from anywhere about $1300-1900 approximately. I want an 18" barrel (maybe 20" would be alright, but want to keep the weight down a little as I am no spring chick). I see there are different models such as Competition Pro 18-20" ($1800-1900), Competition Expert in the $1300-1400 range and maybe some other models. Also, I want an adjustable stock as my wife will also use it and it gets cold in Montana in the winter so may have heavier clothes on. This will probably be the last one I can buy because of retirement. I want to buy good, but I don't need the most expensive rifle available, just a good one. What can you tell me about these different models and what do you recommend? Thanks